The homogeneous group of negative carriers of mobility 1.8 cm/sec. per volt/cm, produced by bubbling distilled water, consists of a normal negative ion in moist air. The positive and negative groups at mobilities +1.0 and -0.95 appear to be due to carriers containing an extra ${\mathrm{H}}^{+}$ and O${\mathrm{H}}^{-}$ ion, respectively. It is likely that the other distilled water groups are formed partly by the breaking of the thin bubble film in uniform fashion, and partly by the evaporation of larger carriers. The presence of electrolytic ions in the bubble film seems to cause irregular rupture, and thus a wide distribution of mobilities. With increasing concentration in solutions more concentrated than ${10}^{-3\mathrm{}}$ mole per liter, the reduced vapor pressure of the carriers containing solute causes the main maximum to shift gradually to lower mobilities (i.e., larger drop sizes). Presence of sucrose in the bubble film appears to provide "nuclei" so that a greater number of droplets are formed than is the case with distilled water. Thus more total charge and more types of carriers are produced. When distilled water is bubbled more violently than usual, the bubble films are more extensively torn into thick fragments by the air blast, so that the positive charges (which on Lenard's theory are in the under layer of the electrical double layer) are more frequently torn off. Hence the proportion of positive charge produced relative to the negative is greater. The less turbulent breaking of the bubble film in the case of gentle bubbling seldom exposes positive charges, so that no positive carriers are produced. The use of supersaturated air in the bubbling blasts inhibits evaporation so that only a wide distribution of carriers of all sizes is observed.

• Received 5 July 1938

DOI:https://doi.org/10.1103/PhysRev.54.528